This invention relates to the field of infrared imaging of films and plates for use in graphic arts.
The use of infrared laser beams in imaging processes has a long history. Braudy, in U.S. Pat. No. 3,745,586, describes a laser transfer process whereby ink coated on the back of a thin film element is selectively transferred to an adjacent material by use of laser energy. Roberts, in U.S. Pat. No. 3,787,210 describes laser blow off using a laser beam for image recording on film. Kasai et al, in Patent No. U.S. Pat. No. 4,214,249 set out the problems of laser beam recording utilizing thermal melting deformation and/or evaporation removal using a laminate of non-metal and metal layers. Oransky et al, in U.S. Pat. No. 4,245,003 describe a laser imageable film with a dried coating of graphite with resin.
Recording films have wide application in the Graphics Arts Industry. They are in use as intermediates in the preparation of various types of printing plates. For instance, they are used as ultra violet (UV) and visible light masks to image pre-sensitized offset printing plates as well as flexographic plates, gravure cylinders and printing screens. They are also used for preparing proofs for inspection before printing. In general, films are in themselves multi-purpose, in that the same material may be imaged with data in a suitable form for a particular type of printing plate and may then be used as a mask so that the plate may be selectively exposed either to UV or visible light, as part of the process of creating the printing master suitable for the particular printing process.
In the field of recording films and their applications in printing, films may now be imaged using digital information. Although silver films predominate in this market, it would be an advantage to have films that do not use conventional silver chemistry, which is a non-renewable resource and which is used with environmentally problematic processing materials. It would also be advantageous if the material could be used in daylight, without taking any special precautions. It is preferable to have the recording material imaged in such a way that no processing is necessary, but if processing must be carried out, it should be simple and fast and if a liquid is required, it should be an environmentally innocuous liquid such as water.
The use of relatively cheap laser diodes in imaging has generated potential solutions to satisfy these demands. Imaging by ablating parts of the masking layer provides the basis for a process that meets the demands of providing almost processless or processless materials and simplifies the mask preparation to a minimum number of steps. To provide adequate performance, the film must have a high Dmax (the optical transmission density of the black areas of the film) and a low Dmin (the optical transmission density in the transparent areas of the film). Such values must relate to the actinic radiation involved when the film is used as a photomask to expose a printing plate.
Although ablation recording films may be produced and have many advantages over conventional films, they have had little impact on the market despite these advantages. One reason for this is that silver-based films are relatively inexpensive. They are made in such large quantities, and as such give economy of scale. Large volumes mean that raw materials can be purchased at minimum prices and long production runs mean relatively low wastage and high productivity. While there may be a significant range of grades of these conventional films, they use common ingredients and this fact contributes to the economy of scale. Thermally ablatable films do not have advantages of economy of scale because of market limitations.
A similar situation exists with infrared ablatable waterless and conventional wet printing plates of various types that are produced for imaging. The same advantages as for thermally ablatable film may be applied to the use of ablatable printing plates, namely, daylight stability, no processing other than harmless solutions etc. The relatively low quantities manufactured compared to non-digital, conventional presensitized plates gives the latter a cost advantage due to economy of scale.
An example of a waterless thermally ablatable plate is that sold by Presstek under the name of Presstek Pearl plate. U.S. Pat. No. 5,339,737 to Lewis et al describes infrared ablatable offset platesxe2x80x94both for waterless printing and for wet conventional offset printing. At present, the Presstek Pearl plate is as much as four times the cost of the cheapest presensitized offset plate and suffers from the same problems of economy of scale described above.
A further example of the contrast between price of conventional printing members and ablatable members is concerned with flexo printing, where patents such as U.S. Pat. No. 5,262,275 to Fan describe flexo plates imaged by infrared laser ablation. Such plates are far more expensive than conventional flexo plates.
One working in the Graphics Arts Industry and using films and plates has to stock a wide range of products such as films and printing plates. Stocking such a range is costly.
Thus, it would be desirable to provide a graphic arts tool that would provide a solution to economy of scale for infrared ablatable graphic arts products.
Accordingly, it is a broad object of the present invention to overcome the problems of the prior art and provide solutions to economy of scale for infrared ablatable Graphics Arts products by a novel modular approach of using common ingredients and by combining functions to produce multipurpose materials with synergistic advantages over the component products from which they have been derived. This is done by combining the properties of a photomask film with those of a printing plate, so that the same material can be used as a film or a plate or can function as both to produce a plate with proofing functions.
In accordance with a preferred embodiment of the present invention there is provided a dual function printing member usable both as a printing plate and a recording film, comprising:
a transparent substrate; and
a coating on a top side of said substrate, said coating comprising at least one layer, wherein said coating has a measured optical density of at least 3.0 both in visible and UV light and wherein the uppermost surface of said at least one layer of said coating is scratch-resistant.
In addition, there is provided a method of producing a dual function printing member for use as both a printing plate and a recording film, comprising:
providing a transparent base layer;
applying a coating on top of said base layer, said coating comprising at least one layer, wherein said coating has a measured optical density of at least 3.0 both in visible and UV light and wherein the uppermost of said at least one layer of said coating is scratch-resistant; and
imaging said coated base layer.
Furthermore, there is provided a graphic tool constructed from selected members of a group of modular components said group comprising:
substrates from the group of: polyester and aluminum; and
ablatable coatings from the group of: carbon black, UV absorbing dye, amino resin, nitrocellulose resin and cross-linking catalysts,
wherein each tool functions as at least one of a film and a plate;
and each of said tools comprises:
a substrate; and
at least one ablatable coating.
Other features and advantages of the invention will become apparent from the following drawings and the description.